correct the annotation of param
correct the annotation of param

In the function trove.instance.service.py,
there is a function has four params,
the first three params's annotation is accurate，
but the last param is incorrect,
so I correct it for others

Change-Id: I1e910c5466861550704419d85d59d0da2e5b7b0f

fabian4/trove,openstack/trove,mmasaki/trove,redhat-openstack/trove,mmasaki/trove,cp16net/trove,mmasaki/trove,zhangg/trove,hplustree/trove,fabian4/trove,hplustree/trove,redhat-openstack/trove,fabian4/trove,openstack/trove,cp16net/trove,zhangg/trove,cp16net/trove,redhat-openstack/trove